Transmit node detection by a receiver in a shared access LTE environment

Abstract

Presented herein are mechanisms to reduce collisions in deployments with Wi-Fi and Shared Access LTE (SAC-LTE) equipment as well SAC-LTE equipment from multiple operators. The mechanisms enhance the baseline energy detection mechanism by incorporating methods to decode cross-technology physical layer elements and media access control (MAC) layer elements in the Wi-Fi system to elements in the SAC-LTE system. The methods described improve the detection potential for transmitters, thereby reducing chances of cross-technology collisions.

What is claimed is: 
     
       1. A method comprising:
 at a first wireless device, obtaining data to be wirelessly transmitted in a transmission burst according to a first format over a shared spectrum; 
 detecting a wireless preamble to a wireless transmission in a second format on the shared spectrum, the wireless transmission being transmitted from a second wireless device; 
 decoding the wireless preamble; 
 determining a minimum time to defer access to the shared spectrum based on the decoded wireless preamble; 
 adjusting an energy detection threshold based on the decoded wireless preamble; 
 determining whether the shared spectrum is free based on the adjusted energy detection threshold; and 
 responsive to a determination that the shared spectrum is free, transmitting the data in the transmission burst over the shared spectrum after deferring for at least the determined minimum amount of time so as to minimize interference between the transmission burst in the first format and the wireless transmission in the second format from the second wireless device. 
 
     
     
       2. The method of  claim 1 , wherein the first format is a Shared Access Long Term Evolution (SAC-LTE) standard and the second format is an IEEE 802.11 standard. 
     
     
       3. The method of  claim 2 , wherein the wireless preamble comprises a Physical Layer Convergence Procedure (PLCP) header. 
     
     
       4. The method of  claim 3 , wherein decoding the wireless preamble further comprises determining a duration of the wireless transmission from the PLCP header. 
     
     
       5. The method of  claim 4 , further comprising transmitting a message configured as a Clear-to-Send to Self after the duration of the wireless transmission. 
     
     
       6. The method of  claim 5 , further comprising deferring access to the shared spectrum for a randomly determined backoff period after transmitting the message configured as a Clear-to-Send to Self. 
     
     
       7. The method of  claim 2 , wherein decoding the wireless preamble comprises one of monitoring a Request-To-Send/Clear-To-Send (RTS/CTS) exchange or decoding a Media Access Control Protocol Data Unit (MPDU), and further comprising determining a network allocation vector including a duration of the wireless transmission. 
     
     
       8. An apparatus comprising:
 a transmitter configured to transmit signals in a shared spectrum in a first format; 
 a receiver configured to receive signals in the shared spectrum in the first format and in a second format; 
 a modem configured to modulate signals and demodulate signals; 
 a processor configured to:
 obtain data to be wirelessly transmitted in a transmission burst according to the first format over the shared spectrum; 
 detect a wireless preamble to a wireless transmission in the second format on the shared spectrum via the receiver, the wireless transmission being transmitted from a second wireless device; 
 decode the wireless preamble; 
 determine a minimum time to defer access to the shared spectrum based on the decoded wireless preamble; 
 adjust an energy detection threshold based on the decoded wireless preamble; 
 determine whether the shared spectrum is free based on the adjusted energy detection threshold; and 
 responsive to a determination that the shared spectrum is free, cause the transmitter to transmit the data in the transmission burst over the shared spectrum after deferring for at least the determined minimum amount of time so as to minimize interference between the transmission burst and the wireless transmission from the second wireless device. 
 
 
     
     
       9. The apparatus of  claim 8 , wherein the first format is a Shared Access Long Term Evolution (SAC-LTE) standard and the second format is an IEEE 802.11 standard. 
     
     
       10. The apparatus of  claim 9 , wherein the processor is configured to decode the wireless preamble as a Physical Layer Convergence Procedure (PLCP) header. 
     
     
       11. The apparatus of  claim 10 , wherein the processor is further configured to decode the wireless preamble by determining a duration of the wireless transmission from the PLCP header. 
     
     
       12. The apparatus of  claim 11 , wherein the processor is further configured to cause the transmitter to transmit a message configured as a Clear-To-Send to Self message after the duration of the wireless transmission. 
     
     
       13. The apparatus of  claim 12 , wherein the processor is further configured to defer access to the shared spectrum for a randomly determined backoff period after causing the transmitter to transmit the message configured as a Clear-to-Send to Self. 
     
     
       14. The apparatus of  claim 8 , wherein the processor is configured to decode the wireless preamble by one of monitoring a Request-To-Send/Clear-To-Send (RTS/CTS) exchange or decoding a Media Access Control Protocol Data Unit (MPDU), and wherein the processor is further configured to determine a network allocation vector including a duration of the wireless transmission. 
     
     
       15. A method comprising:
 at a first wireless device, obtaining data to be wirelessly transmitted in a first Shared Access Long Term Evolution (SAC-LTE) transmission burst over a shared spectrum; 
 detecting a second SAC-LTE transmission burst from a second wireless device on the shared spectrum; 
 decoding a reference signal in the second SAC-LTE transmission burst; 
 determining a minimum time to defer access to the shared spectrum based on a duration of the second SAC-LTE transmission burst indicated in the decoded reference signal; 
 determining access to the shared spectrum based on system information in the decoded reference signal, the system information indicating a wireless network operator supporting the second wireless device; 
 adjusting an energy detection threshold based on the decoded reference signal; 
 determining whether a channel on the shared spectrum is free based on the adjusted energy detection threshold; and 
 responsive to a determination that the channel on the shared spectrum is free, transmitting the first SAC-LTE transmission burst over the shared spectrum so as to minimize interference between the first SAC-LTE transmission burst and transmissions from the second wireless device. 
 
     
     
       16. The method of  claim 15 , wherein the reference signal comprises at least one of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Cell-Specific Reference Signal (CRS), a Channel State Information Reference Signal (CSI-RS) or a Discovery Reference Signal (DRS). 
     
     
       17. The method of  claim 15 , wherein the reference signal is decoded to determine a Physical Layer Cell Identifier of the second wireless device. 
     
     
       18. The method of  claim 17 , wherein the first wireless device is supported by the wireless network operator and further comprising coordinating transmission of SAC-LTE frames over the shared spectrum using a channel on a licensed spectrum. 
     
     
       19. The method of  claim 15 , wherein the first wireless device is not supported by the wireless network operator, further comprising transmitting the first SAC-LTE transmission burst on a separate channel on the shared spectrum, the separate channel being different than a channel used by the second SAC-LTE transmission burst. 
     
     
       20. The method of  claim 15 , further comprising measuring a signal strength of the second SAC-LTE transmission burst and adjusting the energy detection threshold based on the measured signal strength.